1. Field of the Invention
The present invention relates to a coupling apparatus to transfer power, a development cartridge and an electrophotographic printer having the coupling apparatus.
2. Description of the Related Art
Generally, an electrophotographic printer such as a laser printer or a photocopying machine has a development cartridge for forming an image. The development cartridge has a built-in toner cartridge for supplying toner, which is a development agent, and a rotatable photosensitive drum. The photosensitive drum forms an electrostatic latent image corresponding to a desired image by a light projected from a laser projection unit. In addition, a predetermined image is formed as toner supplied by a toner supply means is clung to the formed electrostatic latent image. The toner image formed on the photosensitive drum is transferred to a paper passing through the photosensitive drum and a fixing roller, and is printed.
The development cartridge is a disposable article that should be changed when the toner, which is filled inside, is consumed. Therefore, the development cartridge is removably connected with a printer body. Power can be transferred to the development cartridge from a predetermined driving unit of the printer body through a coupling apparatus when being installed in the printer body. In other words, the coupling apparatus for driving the photosensitive drum and a roller for supplying the toner is provided. One example of the coupling apparatus is shown in FIG. 1.
Referring to FIG. 1, the coupling apparatus has a slave coupler 2 disposed at one end of the photosensitive drum 1 of the development cartridge. The coupling apparatus also has a driving coupler 3 disposed in a direction of the driving unit for transmitting the driving power to the slave coupler 2. The slave coupler 2 has bar-type ribs 2a that protrude by predetermined intervals at an inner circumference of a cylinder of the slave coupler 2. Moreover, the driving coupler 3 has bar-type ribs 3a that protrude at a predetermined interval at an outer circumference of a cylinder of the driving coupler 3. Accordingly, when the driving coupler 3 is inserted into the slave coupler 2, the ribs 3a are placed between each of the ribs 2a. When the driving coupler 3 is rotated, the ribs 3a and 2a contact each other, and the driving power of the driving coupler 3 is transmitted to the slave coupler 2, thereby drawing the development cartridge.
The above coupling apparatus has a gap between the slave coupler 2 and the driving coupler 3 due to errors generated during manufacturing and assembly. Specifically, the gap is generated between an inner diameter of the slave coupler 2 and an outer diameter of the driving coupler 3. Rotation centers of the couplers 2 and 3 differ because of the gap. When the couplers 2 and 3 are rotated about the different rotation centers, a rotation velocity and a rotation force generated from the driving unit is not exactly transmitted to the development cartridge. In this case, an accuracy of the image printed on the paper is deteriorated as the rotation velocity and the rotation force of the photosensitive drum becomes inconsistent.